The present invention relates to an interface module for a host such as a digital television decoder, permitting to process information from the host in a manner subject to a conditional access system comprising authorizing means whereby a user justifies his access rights.
The invention also relates to a decoder integrating such module.
The invention finally relates to a method of processing information from a host capable of being used in the interface module.
The invention is particularly suitable for application in decoders for the reception of digital television programs. The host considered here, however, may also be constituted by other types of decoders, or even, for example, by a computer.
With the development of digital television, the use of decoders capable of receiving signals corresponding to television programs and of transmitting them to a television set after processing into an intelligible format, has become wide spread.
Authorization means comprising chip cards, for example, whereby the user justifies his access rights to programs, are often used.
If the user is recognized and if his rights are identified, processing of the television program signals occurs within the decoder. Currently, specific conditional access systems are used for such processing. From a practical point of view, this is software supplied by the digital television operator and permitting decoding of the signals sent or transmitted from a server to the user.
Initially, distinct decoders for each operator have been proposed, each comprising its own conditional access system.
To satisfy the user holding subscriptions with different operators, decoders comprising a plurality of conditional access systems have been provided. For each conditional access system, a distinct module is necessary in this case, each for cooperation with a specific chip card of the user.
To illustrate the state of the art thus exposed, EP-A-0562295 discloses an apparatus wherein a plurality of card readers are connected to and controlled by a single processor A particular supply unit which is controlled by the processor, feeds the card readers with appropriate voltages.
Document WO-A-97/18656 discloses a system and method permitting to select one of a plurality of signals transmitted by direct television broadcast satellites A conversion box, or decryption device, is equipped with a plurality of different decryption chip cards, which are all simultaneously introduced into the conversion box.
Further, from document EP-A-0696141 a system for controlling different conditional access systems is known, such systems transmitting video, audio and data services to receivers adapted for such services, each conditional access system coding the service to be transmitted within the system, the system sending the coded encryption keys necessary in the receiver and sending authorization messages.
The first mentioned document is not a response to the current needs in presence of a multiplication of conditional access systems since it permits use of a single encryption system only.
Although the second document permits the use of a plurality of decryption systems, it multiplies the number of card readers, each reader being associated with a given decryption, not being adaptive. The third document teaches an elimination of chip card modules, which, however, are used in the environment of the invention In addition, it fails to provide any identification means for identifying authorization means of the user (that may include his chip cards).
Consequently, such devices are of limited applicability and fail to permit a convenient manner of use.